The invention relates to a template aid for a draftsman which makes it simple to crosshatch and section - even to squarehatch - and to provide lettering guide lines. While many prior art structures are known for performing the general function of the present invention, such as those shown in U.S. Pat. Nos. 1,131,962, 2,674,803, and 3,142,906, (also see the Braddock-Rowe triangle, and Ames lettering instrument), it is believed that none of these prior art devices provides a drafting instrument that is as simple and inexpensive as that according to the present invention, while providing numerous different spacings of crosshatching or guide line lines as the present invention.
The drafting instrument according to the present invention comprises an equilateral polygon-shaped sheet having "x" straight-edged sides wherein "x" is an integer larger than 2, a plurality of equilateral polygon-shaped openings formed in the sheet, each opening having "yx" straight-edged sides wherein y is a positive integer, the openings being disposed with respect to the sheet straight-edge sides so that for each opening there is a line perpendicular to a straight-edged side of the sheet that bisects an apex of the opening, and the plurality of openings disposed in at least one series, in each series the distance from the apex of each opening to a corresponding apex in an adjacent opening being a constant throughout the series, relative to a given straight edge of the sheet. The straight edges of the sheets are adapted to be disposed against a T-square or the like, and since the openings in the sheet are formed by polygons, the pencil tip is firmly and accurately located in an apex of the polygon-shaped opening, rather than in a round hole as provided in common prior art structures. By providing a number of series of openings in the sheet, and by providing different constant distances between the openings from series to series relative to each sheet straight edge, an instrument is provided which allows a large number of different spacings between lines to be drawn therewith, which different spacings may be selected merely by simply turning the sheet from one straight edge to another. No moving parts are provided to achieve the great flexibility in crosshatch line distances according to the present invention.
According to a preferred embodiment of the present invention, the sheet is triangular, and the openings formed in the sheet also are triangular, at least two series of openings being provided, and therefore six constant distances being provided, each distance being different.
It is the primary object of the present invention to provide a simple drafting instrument for drawing, hatching and lettering lines of constant readily selectable different spacings without utilizing any moving parts. This and other objects of the invention will become clear from an inspection of the detailed description of the invention, and from the appended claims.